Dynamic Gamma Spectral Measurements of Primary Coolant and Piping at Various Operating Nuclear Power Plants

An on-going EPRI-supported project involves the use of a collimated CZT gamma spectroscopy detector for quantitative measurements of the gamma spectra from primary coolant piping at various times and locations at several operating NPPs. An automatic system − the Data Analyst − takes the spectra from the CZT, and analyzes it on a continuing repeating basis. Measurements are taken simultaneously covering different elapsed times; e.g. 10 minutes for viewing short dynamic events, and 10 hours for low detection limits. The detector is calibrated using the ISOCS mathematical efficiency calibration software, which allows the activity to be computed for a radioactive fluid inside the pipe, or radioactive surface contamination inside or outside the pipe. Measurements have been taken during the reactor shutdown cycle, during the startup cycle, and during continuous full power operations. Examples from these deployments and potential future uses for this technology are described